For example, when information, such as a product illustration for an exhibit, is displayed in an exhibition hall exhibiting products or the like, the following are performed because the information cannot be attached directly to a wall, a pillar, or the like of the hall. In a case where there are partitions provided for respective exhibitors, the information is fixed with an adhesive tape or the like by utilizing the partition. On the other hand, in a case where there is no partition or the like, a notice board is brought in near the exhibit in the hall, and the information is displayed on the notice board. However, if the information is displayed through such methods, there occur various problems, such as the remains of the adhesive tape on the partition, and reduced space in the hall due to the notice board thus brought in.
Further, for example, in the case of displaying information outdoors temporarily, such as a direction guide for giving test takers directions to a test site at university or the like, typically, a simple signboard is prepared, and the displaying of the information is performed utilizing a gatepost, an outer wall of a building, a tree, a simple stake, or the like at a key location. However, it is troublesome to keep the prepared signboard in storage, and hence the fact is that the preparation and discarding of signboards are repeated every year. Thus, the displaying of information material through such a method poses various problems including wasting of wood etc. and efforts used therefor.
Further, for example, in a case where ventilation is provided indoors by introducing outside air indoors in a building like a house, there is provided a dust-collecting/ventilation system including: a ventilation unit for supplying purified outside air to respective indoor rooms and collecting air in the respective rooms to thereby discharge the collected air outdoors; and a dust collecting apparatus connected to an outside-air inlet of the ventilation unit, for collecting powder contaminants, such as dust and pollen, in the outside air introduced from the outside-air inlet. However, in the case of a conventional dust collecting apparatus used in the dust-collecting/ventilation system of this kind, if the dust collecting apparatus is a large-size apparatus, such as a cyclone dust collecting apparatus (Patent Literature 1), it is difficult to secure a set-up space therefor, and also, maintenance of filters imposes a significant load. Further, if the filters are such simple dust collecting filters that are set up at the outside-air inlet, there occurs a problem that powder contaminants cannot be collected sufficiently because of insufficiency of a dust collecting function.
In addition, in the case of such a dust-collecting/ventilation system that is used in a building, the around-the-clock (all-day) operation may be needed depending on the use of the building or the surrounding environment thereof. In this case, apart from the problem of the dust collecting apparatus itself, there is also another problem of how energy for causing the dust collecting apparatus to function is secured.
Further, like the above-mentioned cases of the exhibition/information apparatus and the dust collecting apparatus, there are similar problems with a plant growing apparatus such as a seedling raising box, which is set up outdoors and is used for raising plants like rice seedlings, bean sprouts, and radish sprouts, and fungi like Flammulina velutipes and Chinese mushroom.